"All In" is a story about a passion for success, victory and defeat in business and at the casino, and a love sorrowful and pure.

Kim In-ha (Lee Byung-hun) is an orphan and grows up with gambler Kim Chi-su. He falls in love with Min Su-yeon (Song Hye-gyo) and makes friends with Choi Jeong-won (Ji Sung), the son of hotelier Choi Do-hwan (Lee Deok-hwa). Jeong-won becomes In-ha's best friend, he meets In-ha's girlfriend Su-yeon, and falls in love with her too.

In-ha is accused of murder by Jeong-won's father and makes an escape to the United States. In Las Vegas he meets a teacher of card games and becomes a professional gambler. After he wins the World Poker Championship, he returns to Korea to run a casino and hotel business. Back home, he contends for victory and success with his friend but rival, Jeong-won.